1. Field of the Invention
This invention relates to a Stokes parameter measurement device which measures the state of polarization of signal light or other light, and the measurement method of same.
2. Description of the Related Art
Stokes parameters are parameters which represent a state of polarization. When measuring Stokes parameters, the incident signal light is split into four rays using a splitter means such as a beam splitter, half-mirror, or filter; each of the signal light rays is given a different polarization and phase by means of a half-wave plate or other polarizer and a quarter-wave plate or other phase shifter, the optical components of each of the split signal light rays are subjected to photoelectric conversion using photodetector elements, and operations are performed on the electrical components obtained by photoelectric conversion to obtain the Stokes parameters. The configuration of a Stokes parameter measurement device such as that described above is disclosed in Japanese Patent Application Laid-open No. 6-18332.
In such a conventional Stokes parameter measurement device, a beam splitter, half-mirror, filter, or other device is used as splitter means to split the incident light. Using such splitter means, because the incident light is split by means of interference, polarization fluctuations and a PDL (polarization-dependent loss) occur. As a result, there is the problem that high-precision measurement of Stokes parameters is difficult.